Green Thoughts: There is good grass and there is bad grass

For centuries, cultures around the world have described animal diseases related to grasses. "Drunken horse grass" induced wobbling and possible death in China and Mongolia. "Sleepygrass" caused horses to become comatose for days in New Mexico, while in much of the remaining U.S. the phenomenon became known as "ryegrass staggers." Reproductive problems, weight loss, and general unhealthiness were other symptoms of these mysterious disorders.

By the late 1800's, the link between grasses containing something called an endophyte and animal disease was just beginning to be understood among livestock ranchers, horse owners, and sheepherders.

For those of you not into four-legged agriculture or microbiology, an endophyte is a microscopic fungus that, as the name implies, lives inside a grass plant.

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Very little of the fungus exists in the roots, with more in the stems and leaves. As the story slowly unfolded, a researcher working with sheep and endophytic tall fescue grass varieties in New Zealand in the 1940's noticed that insects, particularly the Argentine stem weevil, didn't feed on the endophytic grasses but devoured those without endophytes.

With that observation and research up to the present day, a benefit to lawn owners was found and the endophyte became the darling of the turfgrass breeders.

Today, many lawn grass varieties contain endophytes for insect resistance. While they don't discourage root-munching white grubs (now that would truly be a miracle!) they do reduce feeding of surface insects, including chinch bugs, armyworms, and sod webworms.

If a lawn has been devastated by chinch bugs, for instance, the use of grasses containing endophytes when re-seeding makes sense, and is an example of the type of integrated pest management called biological control.

Most fescue species and perennial ryegrasses can contain endophytes, while Kentucky bluegrasses do not, although researchers have been working on this, too. Packages of grass seed should be clearly marked, often with the phrase "endophyte enhanced" on the label. This marking is necessary not only to ensure you get the endophytic grasses you desire, but to also aid the farmer in keeping endophytes out of the pasture. Luckily, lightly grazing dogs and cats are unharmed by endophytes. The first turf-type perennial ryegrass containing endophytes was named 'Repell,' and currently there are dozens and dozens of newer varieties available.

While the amount of endophyte in grass plants persists over time, it declines in seed, so buy the freshest seed possible. Endophytes can persist in stored seed for up to two years when held at 43 F, and slightly longer at colder temperatures. In addition to insect resistance, endophytic grasses have been noted to be more vigorous under high heat, drought, and low fertility conditions than the same varieties without endophytes. This is because, at least in part, endophytic grasses have more tillers (stems) and roots. This also makes them more competitive with weeds. Admittedly, endophytic grass seed might cost slightly more, but the benefits justify the expense. Just don't let a horse graze on your endophyte-enhanced lawn!

David Chinery is educational director of the Cornell Cooperative Extension of Rensselaer County. Write to him at dch3@cornell.edu